Soloontario

It is time to pull the trigger on some tires for 2 different sets of wheels for the track this year. I am used to running the same size tires front and rear on a Camaro with a fair # of suspension mods but obviously zero camber out back. I have been comfortable with all R comps but found that high performance streets could overheat at the rear, at least on slower tracks.

I now own a 2004 C5Z. I hear some Vette owners say running a square setup is fine while other say that the factory designed the car for a staggered setup and it should stay that way. Please note that I will be on a completely stock Z06 suspension. I am used to trying to maximise neg camber up front and could never get camber in the rear.

My obvious concern is too much oversteer at the wrong time, in particular corner entry. Can this be tuned out with rear end toe adjustments? I do not have the luxury of changing rear bars or shocks without changing class in our Mobil 1 Time-attack series.

GettReal

I have an 01 C5. I'm on Moton coil overs, Hotchkiss sways, Poly bushings and metal end links so not really stock suspension.... but one of my track wheel/tire set ups is a 300/18 or a 305/18 square set up and I don't have any issues with oversteer. I run about -2 camber up front and the set up is perfect. The Pro is once you know the wear patterns of all 4 tires on a certain track you can rotate and extend the life of your tires. I run at Mosport and Watkins Glen and never experience oversteer.

geerookie

As far as I'm concerned there are no cons to a square setup. The factory staggered setup has a ton of understeer. With a square setup it is more balanced with a bit of overseer but that is usually because the turn in is sooooooo much better. Any unsettled feeling can be tempered with a bit of extra toe in in the rear.

RacePro Engineering

Hi Dave,

We beat this question to death a little while ago:
http://forums.corvetteforum.com/auto...ce-wheels.html

The frequent misconception is that a "square setup" implies that one needs to run a narrower wheel/tire in the rear. We think of it the "other way" -- it gives one MORE grip at the front, not less grip at the rear.

Ed

kmagvette

I have been running square for five years. On a high lateral-g track you will have a fender rub up front if you run anything wide. I carry a file to help right size the fenders...they eventually have the right size opening. Currently I run a 305/660/18 setup on 18x11 wheels...and spare track wheels are C5Z 18x10.5 rears...get a little more shoulder wear on these, but not too bad.

kmagvette

I have been running square for five years. On a high lateral-g/compression track (like Watkins glen) you will have a fender rub up front if you run anything wide. I carry a file to help right size the fenders...they eventually have the right size opening. Currently I run a 305/660/18 setup on 18x11 wheels...and spare track wheels are C5Z 18x10.5 rears...get a little more shoulder wear on these, but not too bad.

John Shiels

Fenders will cut through your tires. Better to just cut them.

Jason

The only cons to a square set-up is you can not run with TC/AH on.

Jason

Fixed.

Soloontario

I have tended to develop a chicken"S%&# type of driving style with the Camaro. I set up a soft rear end, have crappy corner entry, fairly late apex but early throttle application and quite stable and fast corner exit. Don't mind oversteer on corner exit but not particularly happy with it on corner entry. If the rear toe-in (a luxury I'm not accustomed to) will work that sounds great.

How big front tires do you guys run up front with stock Z06 18 X 10.5 rims ?

L98Terror

Why not? I have

I ran my stock 2003 Z in TTA with a sq set up 17/275s all around, I actually prefered it. Was the first TTA car in the 1:33s at Mid Ohio, I also set the TTS Track record at 1:31.1 in a Z06 with a sq set up 315s all around.

I'd say it works pretty good.

Now with the 275s you really get that slip angle going but the car is very balanced

L98Terror

315s

C5ZEE06

sorry to hijack but this is a closely related issue..plus Im just about to head out to the alignment rack so......

anyone willing to suggest some good alignment specs for a square set-up on a dedicated C5Z track / DE / TT car:
- C5Z rear wheels - all around
- 315 Hoosier A's - all around
- T1 bars
- G2 coil-overs
- poly a-arm bushes
- pfadt camber kit (w/ pfadt FU a-arm pins - so basically unlimited negative camber opportunities).

Lots of guys with this basic set-up so..whats been working for you ?

Jason

My car does not like it when I forget to turn the AH/TC off, it goes bat-sheit crazy as soon as I turn. Could just be my car, we keep finding differences.

L98Terror

Mine was doing that when there was play in the bearings, didn't when i first started tracking like that and didn't after replacing all 4

geerookie

Don't confuse unsettled feeling with oversteer. Corvettes tend to have the rear end "dancing" a bit under heavy braking due to the droop on the rear suspension and the inherent camber curve for the rear suspension.

geerookie

I guess it would have to still work in the car to have to worry about it and a race car SHOULD NOT be driven with a street calibation of AH anyway.

geerookie

Hoosier A6 315 front and rear on 10.5 wide wheels w/ 58mm ofset.

geerookie

Thanks

geerookie

The poly bushings make these numbers different. I have full sphericals.

I run
Camber -1.5 to -2.5 front, -1.5 to -2.5 rear (depends on the track)
Toe 1/8" toe out front and 1/8" toe in rear
Caster what ever it ends up but less than 4 or 5 degrees

When I had poly bushings I think I had to run camber at the max I could get which was about -3.5 front and -2.8 in the rear.

IMHO Anything less then .5 degree adjustments are worthless with DOT slicks and most of the time I make full degree changes as you can see from my numbers.